缘管浒苔对赤潮异弯藻的克生效应

The allelopathic effects of Enteromorpha linza on Heterosigma akashiwo

利用共存培养系统研究了缘管浒苔(E nterom orpha linza)新鲜组织和干粉末对赤潮异弯藻(H eterosigm a akash iw o)生长的克生效应。共存实验结果表明,缘管浒苔新鲜组织和干粉末对赤潮异弯藻生长均有强烈的克生效应。同时,研究了缘管浒苔培养水过滤液对赤潮异弯藻的克生作用。赤潮异弯藻在缘管浒苔培养水过滤液的半连续添加方式下生长受到明显的克制作用,但在一次性培养方式下生长未受到明显的抑制作用,说明克生物质的连续分泌是有效克制赤潮异弯藻生长的关键;煮沸的大藻培养水过滤液对微藻的生长无抑制作用,表明克生物质在高温下不稳定和易分解。

Harmful algal blooms （HABs） of the coastal raphidophyte Heterosigma akashiwo have been the focus of many studies, primarily due to the devastating effects this alga has had on the aquaculture industry. Heterosigrna akashiwo is notorious for ichthyotoxicity and widely distributed in the world. Heterosigma akashiwo has caused great economic loss in many countries. Allelopathy is a prevalent natural phenomenon in aquatic ecosystems and also a means of biological control of water weeds. This paper studies the allelopathic effects of the macroalga Enterornorpha linza on the microalga Heterosigrna akashiwo, in order to provide some theoretical proof for biological control of harmful algae blooms. Allelopathic effects of fresh tissue and dry powder of Enterornorpha linza on Heterosigrna akashiwo were studied using coexistence culture systems. Different initial inoculation concentrati-ons （0, 0. 625,1.25, 2.5, 5 and 10 g wet/L） of macroalga fresh tissue and （0, 0. 15, 0. 3, 0. 6, 1.2 and 2.4 g dry/L） of macroalga dry powder were used in both coexistence culture systems. The results of the coexistence assays showed that the growth of Heterosigrna akashiwo was strongly inhibited by fresh tissue and by dry powder of Enterornorpha linza. The cells of Heterosigrna akashiwo died completely within five days at the two highest concentrations （5 and 10 g wet/L） of macroalga fresh tissue. At a threshold level of 1.2 g dry/L of dry powder of Enteromorpha linza, H. akashiwo cells were completely killed when their initial density was lower than 1 ×10^5 cells/ml. The effects of the macroalga culture medium filtrate on the Heterosigrna akashiwo were also investigated to confirm the existence of allelochemicals. The growth of H. akashiwo was not significantly （p〉0. 05） lowered by macroalga culture medium filtrate under initial filtrate addition. On the contrary, the growth of H. akashiwo was strongly inhibited by macroalga culture medium filtrate under semicontinuous filtrate addition. It was speculated that continuous addition of allelochemicals was important to effectively control the growth of H. akashiwo. Heterosigrna akashiwo was not inhibited when inoculated in the boiled macroalga culture filtrate, which suggested that allelochemicals from the fresh tissue of Enteromorpha linza were unstable and degradable at higher temperature. These assays prove that Enteromorpha linza has allelopathic effects on H. akashiwo. These results not only provide insight into the interactions between macroalgae and microalgae in coastal areas but also lead us to isolate and characterize these allelopathic substances in future.